1. Field of the invention
The present invention relates to a sinter and a casting applicable to a part having fire surface irregularities such as a gear, a milling head, a golf club head or a golf club shaft. More particularly, the invention relates to a sinter or a casting comprising a glassy alloy capable of being formed into a non-crystalline bulk-shaped product having a high hardness.
2. Description of the Related Art
Some kinds of multi-element alloy have a property of not crystallizing when a composition is quenched from a molten state, and transferring to a vitreous solid via a supercooled liquid state having a certain temperature range. A non-crystalline alloy falling under this category is known as a glassy alloy. Conventionally known amorphous alloys include an Fe--P--C-system non-crystalline alloy manufactured for the first time in the 1960s, an (Fe, Co, Ni)--P--B-system and an (Fe, Co, Ni)--Si--B-system non-crystalline alloys manufactured in the 1970s, and an (Fe, Co, Ni)--M(Zr, Hf, Nb)--system non-crystalline alloy and an (Fe, Co, Ni)--M(Zr, Hf, Nb)--B-system non-crystalline alloy manufactured in the 1980s. These alloys, having magnetism, were expected to be applied as non-crystalline magnetic materials.
Since any of the conventional amorphous alloys has a tight temperature range in the supercooled liquid state, a non-crystalline product cannot be formed unless it is quenched at a high cooling rate on a level of 10.sup.5.degree. C./s by the application of a method known as the single roll process. The product manufactured by quenching by the single roll process took a shape of a thin strip having a thickness of up to about 50 .mu.m, and a bulk-shaped non-crystalline solid was unavailable. When a bulk-shaped formed product is to be obtained from this thin strip, a sinter is obtained by crushing the thin strip resulting from the application of the liquid quenching process, and sintering the crushed strip under pressure in a sealed space. The sinter produced from the conventional amorphous alloy is porous and brittle, and is not applicable as a part subjected to stress such as a gear, a milling head, a golf club head or a golf club shaft.
Glassy alloys known as having a relatively wide temperature range in the supercooled liquid state, and giving a non-crystalline solid through slower cooling include Ln--Al--TM, Mg--Ln--TM, ZR--Ln--TM (where, Ln is a rare-earth element, and TM is a transition metal)-based alloys developed during the period of 1988 through 1991. Non-crystalline solids having a thickness of several mm available from these glassy alloys have special compositions in all cases and contain rare-earth elements, resulting in a high cost, and no sufficient study is made regarding applications.
The head portion of a wood-type golf club is usually manufactured with a metal such as stainless steel, an aluminum alloy or a titanium alloy as a material, and the resultant metal wood forms the main current in the market. As compared with the conventional persimmon wood, the metal would provide an advantage of a very high degree of freedom in designing the head.
In an iron-type golf club also iron (soft iron), stainless steel, carbon, titanium alloy and various other materials are used for the head.
In a putter-type golf club as well, iron (soft iron), stainless steel, titanium alloy, duralumin and various other materials are applicable.
For the shaft for a golf club, the carbon shaft excellent in lightness and easiness to handle forms the main current in place of the conventional steel shaft. The carbon shaft have advantage of a high degree of freedom in design, and various kinds of shaft are now commercially available, including those for frail women and for professional golfers.
For a wood-type golf club having a head made of stainless steel, it is believed that only a head having a relatively large thickness and a small volume (up to about 220 cc) is manufacturable because of a strength not so-high of the material and a high specific gravity.
An aluminum alloy used for a golf clubhead is generally believed manufacturable into a large head because of a high specific gravity, but inferior to a stainless steel or titanium alloy head in yardage.
A titanium alloy, which is suitable as a material for a golf club because of a high strength and an excellent repellent force, must be fabricated in a vacuum or in an inert gas and the yield is low, resulting in a very high unit cost of a head.
For the iron-type golf club, the head made of soft iron has defects of a relatively large specific gravity and easy susceptibility to flaws.
A stainless steel head, which is excellent in durability, does not permit adjustment if the lie angle or the loft angle, and is kept at arm's length by senior golfers.
A head made of a titanium alloy is defective in that fabrication requires much time and labor, leading to a very high unit cost as described above.
As compared with the above-mentioned metal heads, a carbon head is far more susceptible to flaws and handling must be careful.
A putter-type golf club should preferably be provided simultaneously with appropriate bounce and weight, but a material satisfying these requirements has not as yet been existent.
A carbon shaft for a golf club has generally a configuration in which it comprises an inner layer obtained by aligning carbon fiber groups in a direction, impregnating the same with a thermosetting synthetic resin and forming the same into a tubular shape, and an outer layer available by aligning fine line or filament-shaped alloy groups in a direction, impregnating the same with a thermosetting synthetic resin, and forming the same. The alloy used for the outer layer has an important effect on properties of the carbon shaft. In order to manufacture a shaft light in weight, it is necessary to make the alloy of the outer layer finer, but this results in a lower strength. In order to increase strength, it suffices to use larger alloy lines, but this leads to a larger weight.